People sent human test dummies offshore, where they waited for dolphins. Not too long afterwards, they were sure to arrive; using their genitalia to carry the test dummies down into some specific cave where many other mangled corpses were found; likely raped.
An article I read on the experiment referred to the cave as a "Dolphin rape cave"

A female was once, as per part of experiment, required to live in a house with a low water level. As in, it was slightly submerged. Thanks to this, a dolphin was able to swim around in it and partake in mental excersizes to forward the experiment. However, the dolphin wasn't all to fascinated by these tests, and decided to begin advancing on the scientist. He would neglect all attempts to get him to follow the tests.

Eventually, she decied to pleasure the dolphin, as per his growing advances. This lead to a great breakthrough in the way we now see this subject, as knowing that such a thing is possible. After that, the dolphin began complying to the tests and bonded more heavily with the female client.

Actually, the world record holder is 9 inches flaccid, so he still wouldn't be a winner.
And, I'd know. Oh yeah.
Because I have the statistical obsession with penis size which every small-penised man has.